Conventionally, as an apparatus that utilizes a scanning device of a laser light or the like, there is known a scanning laser radar apparatus, a laser scanner, a laser printer, a laser marker, an object monitoring apparatus, and the like. As an optical scanning actuator that is used in the scanning laser radar apparatus for preventing collision of a vehicle among these apparatuses, a technology is known in which one movable mirror is caused to swing or perform a rotation movement by a motor, light from a laser light source is emitted toward the movable mirror, and reflection light thereof is caused to scan as a probing light (for example, see Patent Document 1).
FIG. 6 is a perspective view illustrating a configuration of a conventional optical scanning actuator. In an optical scanning actuator 31 shown in FIG. 6, base end portions of a pair of leaf springs 34a and 34b that are arranged in parallel in an up and down direction are fixed to a fixing member 33 assembled to a base member 32 (the leaf spring 34b is not shown). Each tip portion of the leaf springs 34a and 34b is fixed to a mirror holder 35 that holds a mirror 36 (shown by a chain double-dashed line in FIG. 6) that reflects light incident from a predetermined light source. At the mirror holder 35 as a movable unit, a pair of coils 37a and 37b are arranged at positions at which they are symmetrical around an origin position of the leaf springs 34a and 34b as a center.
An arc-shaped yoke 38 is fastened to the base member 32. An arc-shaped portion of the yoke 38 consists of a lower side portion 38a and an upper side portion 38b that are parallel to each other, and the lower side portion 38a passes through each opening plane of the coils 37a and 37b. A magnet 39 is fixed to a surface of the upper side portion 38b opposing the lower side portion 38a out of the surfaces of the upper side portion 38b. 
In the optical scanning actuator 31 having the above configuration, the yoke 38 and the magnet 39 form a closed magnetic flux. Therefore, when an alternating current flows in the coils 37a and 37b, the Lorentz force acts on the coils 37a and 37b. The mirror holder 35 that holds the coils 37a and 37b is driven by the Lorentz force, along with which the mirror 36 swings, whereby light scanning is realized.
Patent Document 1: International Publication Pamphlet No. WO 02/008818